Before diving deep into Tezos, let's get to know blockchain first. This module will cover Introduction to the blockchain, how they work and what are the use cases of blockchain.

Introduction

Blockchain is a chain of blocks that acts as a digital ledger. It was introduced in 1991 with the intention to timestamp digital documents so that it's not possible to tamper with them. Later, Satoshi Nakamoto implemented this idea to create the digital cryptocurrency Bitcoin.

<aside> 💡 Know more about the history of blockchain here

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Structure of Blockchain

Blockchain is a distributive ledger on which data is stored and is very difficult to change. It is made up of blocks that are linked to each other by a hash which is unique for every block.

The first block in a blockchain is called the genesis block. A block contains:

• A batch of valid transactions
• Hash of the block - It is a hexadecimal number and is always unique. It connects all the blocks in a blockchain. If the data changes in a block, the hash also changes.
• Hash of the previous block - Every block stores the hash of its previous block.

<aside> 💡 Learn more about the basic working of blockchain here

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How does it work?

The chaining of blocks by their hashes, as described above, makes blockchain immutable. If we change a block, then all the blocks after it will become invalid.

But, nowadays computers are fast enough to recalculate hashes of all the blocks and to make blockchain valid again. Therefore hashing itself is not enough to prevent tampering.

In order to make blockchain more secure, it is distributed over a network, which means valid blocks have to be replicated on all network nodes. Everyone connected to the network has a full copy of the blockchain.

When a new block is created, it is sent to everyone to verify if it is tampered with. All nodes create a consensus and validate a block. If the block validates then it is added to all the nodes.